We all know the classical trope of making a deal with the devil. The mortal applicant desires some worldly possession, knowledge, or power, and is willing to trade his own soul for it.

Picture the devils in this setting as the epitome of Lawful Evil. They don't tell outright lies (but if you misunderstand what they said it's your problem), and they always keep their promise (but they interpret everything in a way it benefits them the most). They have a whole army of lawyers at their disposal.

They don't have as their goal to cause suffering in humans, but they are very selfish and do cause suffering if it furthers their goals. Tempting people to commit sins are among their goals, as it will increase their influence and power. However, the people have to do the evil acts willingly, so all the devils can do is to nudge them towards temptations, they cannot force them. They also never arrive uninvited, their PR rules prohibit cold-calling. The mortal must call out to them to conduct any business.

However, they have a problem. The business doesn't go very well. Too few people are willing to relinquish dominion over their immortal souls for all eternity after their deaths. The price is simply too high for any material gain. To expand the business horizons, the commission of the Infernal Corporation decides to offer their services in more limited packages to appeal to a wider range of customers, with lower prices.

However, what can the prices of the limited services be, if souls cannot be split?

Note: the customer will be properly informed that the deal is done with an authorized agent of the Infernal Domains. The services cannot be for free, both because of the nature of the devils and because the customers would become suspicious. The deal has to be fair, or at least perceived to be fair by the customer.

Discarded ideas:

One idea was to do it as a marketing campaign to increase brand awareness, but people who wouldn't give up their eternal soul, would probably not be convinced to do so after trying out a limited offer. And even if they did, giving something for free would be opposite of the very nature of devils. They are selfish, and they only make a deal if it directly benefits them.

Another idea was used in the Order of the Stick, where a wizard got a significant boost of magical powers for a limited time, and as payment, the wizard had to agree to spend the same amount of time as the duration of the powers, in the custody of the service provider at a later time chosen by the provider. In this case the deal was well worth for the fiends because the wizard was taking part in highly important missions, many of them about preventing evil acts, so a temporary imprisonment could make it impossible to prevent one such evil act. However, in our case, the expected customer base is to be regular humans, without such important missions, so the devils would not gain anything really useful out of the deal.

Note, that the service provider has to gain something tangible and useful out of a deal. Just making the supplicant suffer is in itself not a gain. So no such things as "I will help you in your job interview if you hit your little finger with a hammer".

Humans have free will, and the devils cannot directly force anyone to do anything they wouldn't want to. So "you agree that you will kick a puppy" is not an appropriate payment, as it is not enforceable. (and also not too useful for the service provider)

Currently I'm considering "relinquishing control of your physical body to us for an agreed-upon period of time" as a method of payment. It has the advantage of being less severe than giving up one's immortal soul, and it can also be quantified (more time for larger services, less time for smaller ones), and it can also be very useful for the Lowerarchy. However, it has the disadvantage of still being too scary for most potential customers. Can this payment method be improved upon, or are there better payment methods not yet considered?

$\begingroup$Well if all they want is people to commit sins then that's quite easy. I'm sure there are plenty of people that would murder a person or two if it would got them a good job or even a couple thousand bucks. People are desperate and people (like devils) are selfish.$\endgroup$
– AngelPrayMar 3 '17 at 17:54

4

$\begingroup$The critical questions here are 1) why do they want people's souls? And 2) why do people consider them too valuable to give up for material gain? Once you/we know the answer to these, how to go about sub-letting and sub-dividing souls.$\endgroup$
– RBarryYoungMar 3 '17 at 18:48

4

$\begingroup$I'm not sure that "agreeing to commit a sin" is a bad one, that is, I disagree with your premise. The devils are not forcing them to do so. They're saying "If you want X, do Y. It's OK to choose not to do Y, I'm not taking away your free will. But hey, X might be worth it, eh?" They could withhold payment until the act is performed, as well.$\endgroup$
– MichaelMar 3 '17 at 19:50

2

$\begingroup$One thing you've overlooked in your order of the stick example is that the evils didn't just purchase temporary ownership of the hero's soul: they bought the opportunity to give the hero additional temptations the hero was likely to fall for.$\endgroup$
– HurkylMar 4 '17 at 2:30

6

$\begingroup$"So 'you agree that you will [do X]' is not an appropriate payment, as it is not enforceable." Sure it is: have the person sign a contract. They promise, in exchange for services rendered, to do X by Y date. If they fail to do so (says the fine print), the penalty is the forfeiture of their soul. This doesn't violate the "people have to do the evil acts willingly, the devils cannot force them" rule, because they knew what they were agreeing to when they signed the contract. If they weren't willing to do X, they wouldn't have agreed to it.$\endgroup$
– DLoscMar 4 '17 at 7:47

19 Answers
19

Information

Information is power. Power is information. Set yourself up as a broker of secrets and bribe informants with nuggets of diabolical power or, similarly, promise people information in exchange for them doing things that you cannot do (being lawful and all).

This works especially well if your setting is one where spells are recipes/Words of Power or True Names grant you a measure of control over a being. It also sets you up to have powerful devils essentially being the heads of huge spy organisations, focused on gaining as much exploitable intelligence as possible. Of course, what may be a small price in information for a mortal to pay can be leveraged into a huge opportunity for the spider at the center of the web.

After all, John Doe from the IT department may well sell company secrets in exchange for a date with Laura Smith from finances, and Laura Smith from finances may well sell information about the next quarterly report in exchange for getting a promotion. You can then use the first to get a competitor to help you force the CEO of the company into a seemingly hopeless position (still a fair deal, according to supernal contract law) when hey presto you can give him a tempting offer just before he takes the twenty-story step. And you come already prepared with the appropriate paperwork.

That, of course, is just one small example of how valuable information can be to a suitably savvy underworld representative. Go forth and profit from the idiocy of mortals!

$\begingroup$I wanted to put pyramid schemes on the list of discarded ideas when I started writing this, I just forgot. I was thinking that as the devils are knowledgeable in business-related things, they know a pyramid scheme becomes unsustainable very quickly. They would want some more long term solution.$\endgroup$
– vszMar 3 '17 at 18:21

5

$\begingroup$@vsz Pyramid schemes are great at the top, just not for the suckers at the bottom. Get a wish at the cost of damning 10 other souls, but the fine print says if you don't succeed you forfeit your soul (plus those you did manage to convince to sin too - 7 net souls for one wish). There are always suckers who overestimate their ability to sell and get the benefits - of course if they damn 10 others, isn't their soul damned anyway (regardless of the contract being complete)? Depends on the theology at work here. On a long timescale, population increases, so there is always another sucker born.$\endgroup$
– pluckedkiwiMar 3 '17 at 21:51

5

$\begingroup$@vsz Pyramid schemes are unsustainable if you get too greedy. But if you have patience, you can milk it forever. After all, there's a new sucker born every minute.$\endgroup$
– kingledionMar 4 '17 at 1:16

5

$\begingroup$@kingledion According to the Internet 250 people are born every minute. So only 0.4% of people born need to be a sucker for your statement to be true.$\endgroup$
– AnketamMar 4 '17 at 11:24

1

$\begingroup$@SRM brute force exhaustive search is a perfectly fine sucker-search algorithm. You simply make an offer that's ridiculous enough so that only a sucker would fall for it, and the 0.4% that respond are your "customers". E.g. the reason why "Nigerian inheritance" scams explicitly include the Nigeria connection, have spelling mistakes and don't try to mask themselves as something more plausible is so that they wouldn't have to waste time in "sales follow-up" with non-suckers.$\endgroup$
– PeterisMar 6 '17 at 9:43

There is always a Gangster approach: "One day, I will ask you for a favor..."
The devils could get very specific about what they won't ask for to make the punch of the eventual favor more palatable. If the poor human doesn't get the full scope, well, that's just his too darn bad.

The kinds of favors I'm imagining would be ones that don't have to make much sense to the person carrying them out, but would have long term pass along effects. Terry Pratchett and Neil Gaiman mention this kind of low grade evil in "Good Omens". One of the characters ties up every cell tower in the city for half an hour, causing a wave of antipathy and anger that tarnished every soul for miles around. Not the craftsmanship that a Demon going after a soul would use, but something that would spread evil farther and erode good just a little bit more.

Let's take Joe Blow, who wants the promotion at an energy company. The favor comes due 2 years later when he is asked to fire a young creative guy he doesn't really know during a round of layoffs. Not an explicitly evil act, and not even anything that might go against Joe's nature. This young creative would have created something like a truly efficient photovoltaic cell for 1/3 of the cost, but now he's out of a job. The new cell doesn't come up, we rely on fossil fuels for that much longer, and so on. Joe hasn't really done anything terrible in his own mind, but Evil advances that much more. Even better, Joe gets another promotion making him a very satisfied customer. Word of mouth is the best marketing after all.

For Enforcement, just give a clause about "revocation of any and all benefits gained, plus penalties". for Joe Blow, when he wavers about firing the young creative guy, he is given a vision about how he will lose the promotion, and it will be way worse than what he thought at the beginning of the infernal bargain. He might be losing his promotion amidst a sex trafficking scandal, where he will go to jail. In addition, the mole that he got checked with his new health insurance will turn out to be cancerous. Joe still has free will, but now he will be painfully aware of the consequences of going back on his deal.

Offer shark loan where the soul would be the collateral? I mean it's a nice market segment, because potential clients already lack other assets and would be uninteresting for the banking sector. Such deal is more palatable for mortals, as they do not lose their soul immediately and can just repay the whole loan.

It's a win-win for the Hell:

some people would just give all money back with interest rates (they would be used to make the business model sustainable and self financing)

some people would default on their debt thus their soul would be collected

some people would have to provide some services to repay their debt to Hell (read debt-bondage)

some people would be the perfect clients: they first pay lots of interests but still fail to escape the debt spiral

(I would like to thank all employees of my bank for helping me to create this idea)

A reverse lottery. Slogan: "it probably won't be you". Potential subscribers will be tempted by the knowledge, based on experience with more normal lotteries, that the slogan is accurate. In return for placing their soul at a demonstrably minuscule risk, they get significant and regular tangible benefits. It's so obviously better than the regular lottery that it puts the regular lottery out of business.

Some potential subscribers will object that they don't trust the demons to make a truly random selection of the "winner". The demons will reply that they do their utmost to ensure that their selection really is random, and that it's not as if they have a vested interest in choosing one person over another. As long as they get their soul, they're satisfied. They might also introduce a variant which has no random element whatsoever. Instead, each week the unlucky "winner" will be the person who is most objectively evil among the subscribers. Subscribers will wager that although they might be a little bad, there's no way they can possibly be the very worst out of all the participants.

$\begingroup$I like this idea! But wouldn't taking the most evil person incentivize doing good? It might be better to take whoever does the least evil, with rhetoric about how they're not using their newfound power to its proper potential.$\endgroup$
– DraconisMar 6 '17 at 3:38

1

$\begingroup$@Draconis: Note that as proposed, the devils have absolutely no care for Good/Evil, they just want souls, and therefore picking the most evil is really clever since even evil people often see themselves as "normal" (bias and all...)$\endgroup$
– Matthieu M.Mar 6 '17 at 11:46

$\begingroup$@MatthieuM. True but if people do evil things with the power, they're more likely to get sent to Hell after death even if they aren't picked. The more people doing evil acts, the more souls the devils can eventually get.$\endgroup$
– DraconisMar 6 '17 at 14:52

Add more soul mechanics to your world

At the moment based on what you have told us your world is lacking in things that can be done with souls. However, devils being the crafty sort they are could potentially come up with some more creative things they can do to get partial souls without running into the whole issue of splitting or purchasing part of a soul. Devils after all are rule lawyers I am sure they can find ways to bend the rules of souls without divine forces intervening.

Soul Binding

Daemon the devil has invented a clever method by where he can bind a devil's soul to a human's soul for a temporary (or permanent) period of time. The effects of this can have quite a range depending on how strong the binding is.

There are a number of potential benefits to the devil by doing this. First off if devils can draw power from human souls, then being temporarily bound to one can make them more powerful. Second possible benefit if the devil can experience anything their human experiences, then it can be sort of a vacation. Imagine binding to a human for a few weeks right before they get married and go on their honey moon. They in the most literal sense could live vicariously through a human.

To the human though they might not even notice the devil being bound to them if it is a rather weak binding for a short period of time. This would be a fairly minor price to pay for a small service by the devils.

Soul Tagging

Devils need information and human souls can go places devils cannot (like Heaven). In exchange for services by a devil, the devil puts a tag (listening device if you will) on their soul. Human loses nothing, and if they do make it into a place besides Hell then the devils have a spy in that realm that can potentially relay information back to them.

Soul Farming

When humans breed they create new humans with new souls to inhabit the baby. This is a fascinating process, but unfortunately it can only be produced on Earth. However, devil scientists have devised a way of triggering the soul breeding part without the physical part. The catch is that it must be done on Earth with living humans. So devils buy the rights from humans to be allowed to trigger the soul breeding aspect X number of times. The devils then perform the breeding and farm the new disembodied souls. So the humans still go on with their lives unknown to them that they have spiritual children, while these innocent souls get to be raised in Hell. It would be pitched more along the lines of the person doing a sperm donation, rather than what it truly is.

then make more deals for acts of revenge, causing a slow, gradual taint of the various souls. Small wishes for small "favors".

The "favors" should slowly push the "clients" into more and more sinful behavior. For added points, have a network of events going....

Client A wants something, so as for payment, he needs to steal something from "B"'s store and bring it back to the devil who gives it to "C" in another deal to give it to "D" who just happens to need it.

"D" gets caught and now needs to make a deal with the devil to get out of the mess while "B" comes to the devil (not knowing that "D" was caught) and makes a deal that "whoever stole it gets punished".

"A" is now in the hotseat as "D" has been proven innocent thanks to the help of the devil and the authorities are coming after "A".... and so on.

The way to make this work is that each deal either hooks the person in for more, thus doing more damage to their soul, or gets another "customer" for the devil.

For the ones that just keep the original coming back for more, the wishes should be granted, but create more problems. Not "Monkey's Paw" style, but just irksome enough so that they keep coming back for more.

Part of the contracts should be that no future contract could undo what is done.

Now, for the price of a moderate house, anyone can get away with murder.

The bullet comes complete with a legal contract pledging the formidable legal power of Infernal Corp (who secretly employs almost every living lawyer and all of the dead ones) to defend the purchaser from all human prosecution.
A little advertising and a few successful use testimonials would have people lining up at the corporate offices to buy a bullet or two.

What they do with the bullet is of no interest to the devils, who are only interested in the post-life consequences of their customer's choices. And since most of those customers don't believe in an afterlife anyway,...

The potential LONG TERM costs won't distract them from their purchasing frenzy.

$\begingroup$Only problem with this answer is that the devils are not likely interested in money.$\endgroup$
– AnketamMar 3 '17 at 21:01

6

$\begingroup$@Anketam it’s not clear, but I think the point is that consequence free refers to secular while-living prosecution. But they get people to commit murders, which affects their soul and afterlife.$\endgroup$
– JDługoszMar 3 '17 at 21:08

$\begingroup$Okay, I see where you are going with this idea now.$\endgroup$
– AnketamMar 3 '17 at 21:14

4

$\begingroup$The fact that devils aren't interested in money is actually the beauty of this answer. When the customer buys it, it seems like a fair deal. (100 grand is expensive, but it makes sense given the outcome!) Hell, they could offer financing plans.$\endgroup$
– MichaelMar 3 '17 at 21:38

2

$\begingroup$"Infernal Corp (who secretly employs almost every living lawyer and all of the dead ones)" ... that was gold :D$\endgroup$
– hmijailMar 6 '17 at 10:12

Two words: Pawn broker.
Here's how the system works. You come to the pawn broker with expensive item X that you don't want to give up, but your back is against the wall. Broker says, "Tell you what... I'll give you $30 now at 0% interest. You let me keep X, and you pay me back within 3 days. If you pay me back, you get X back. You haven't sold it, just let me hold onto it." So you think, "Well, payday is in 2 days... and I need the money now." And you say, "Yes. I'll do it."

Two days later you pay back the money. You get X back. All is good.

You do it again, and again, and again, always getting just enough to stretch to the next thing. But the thing is, the broker knows he's sitting on something worth a lot more than $$30. And he's going to be nice about it. Each time you come back, he says, "Hey, there's a lot of demand for these things. Why don't I give you $40 this week." And you're fine with that. But it keeps going up, and you get used to having that extra cash, and soon, it's brushing up against the complete value of your paycheck, and you don't notice when it slips over that line, and now it's 3 days later and the broker looks at you and says, "Sorry, man, not my fault. Another guy came in, took one look at X and snapped it up. You should've been more careful with your money. Bye."

In this case, X is the person's soul. It works with any valuable thing by ratcheting up the value offered for the thing. You never have to divide up the soul, and, in the end, you actually can end up buying the soul for WAY less than it is actually worth. There's your lesser Faustian bargain.

And that's before we get to modern accounting practices of hedge funds, credit default swaps, and short selling. The devil has many tools, courtesy of modern finance.

$\begingroup$@DLosc I think this answer is similar to Shadow1024's answer. Instead of the Faustian deal where the human gets something for their soul, the human gets something in return for the devil's pawn holding their soul as collateral until they repay (with interest). The devil's pawn shop gets lots of money from some humans, and souls from human who can't repay. A human avoids losing a soul when deal the is made (so deal is less scary, since of course they will repay), but devil still ends up with more souls than otherwise because some humans will default.$\endgroup$
– Mark RipleyMar 4 '17 at 10:05

$\begingroup$@DLosc Mark has it right. The question was asking for a way to make lesser deals without splitting the soul while avoiding buying the soul outright, which the seller would never do. The pawn shop is exactly such a lesser Faustian bargain.$\endgroup$
– SRMMar 4 '17 at 10:25

One thing that devils could ask for are for the person to preform actions that put other people's souls at risk. Note that doing this will actually taint the deal makers soul as well so the devil is getting two benefits instead of one.

Like put something valuable out where it would be the target of theft by people who are decent (bonus for kids) to see if you can get someone to start down that path.

Bring 3+ people to the devil to make deals. This is especially good if the person is being used to get near someone more important.

A variation of the above is to have the person perform a series of actions that back someone else into making an even bigger deal with the devil. To max that one: start a feud between two groups so the devil can make deals with members of both groups.

It could even be as simple as in the morning going to work, cut people off in traffic and when the light turns green, sit there until it turns yellow again and then cross the intersection. Thus you cause a number of people to be angry and, maybe, make bad decisions throughout the day.

The trick is not to force anybody to do anything, but to endanger their souls in ways that they themselves can control through willpower. You want to improve your love life? Well obviously, an increased libido is an advantageous part of the deal – of course you know that your interests will be slightly skewed towards people who are already married. But you can compensate for that, you can just ignore the temptation. After all, you're a good person, right? And you just actually might be a good person. Maybe only 5% of such contracts lead to actual adultery. But if you sell enough contracts, 5% is more than enough. It's a psychological fact that people underestimate risk factors when they have some control over them. (Edit: Differences in risk evaluation depending on whether or not you are in control are a part of Optimism Bias: It's the cognitive effect that e.g makes people think that they are less likely to crash, if they themselves are driving the car.)

This isn't all too different from the way some actual drugs work. Cortisol for example: Sometimes it makes people irritable and aggressive, sometimes it makes them euphoric. It almost always makes them hungry. It's perfectly possible for a disciplined person to resist these temptations – but the overall likelihood of them doing something bad is increased.
So basically, instead of your doctor prescribing you cortisol, you could go to a devil and buy your health with temporarily increased susceptibility to wrath and gluttony. You know that your illness will vanish, but for a few months you will perceive a lot of things people do around you as irritating, as possible personal insults. Someone making slight eating noises in your vicinity will feel like them moving an inch away from your face and chewing with an open mouth, while staring into your eyes and grinning. You don't have to punch them in the face – but damn will you want to. You're fairly certain that they aren't trying to insult you, that this is just the demonic influence speaking… but… GAH!

The more certain you are of your own virtue and willpower, the more likely you will be to risk such contracts. And hey, if you only sin slightly while under their influence, if you only give into the temptation little bit… You will probably be able to compensate for that…

Edit 2 to try to incorporate criticism: From the Devils' perspective this might not be considered as giving something away for free, but more akin to a potentially risky financial transaction. A bit like the stock market: You invest in someone's sin, hoping to see it flourish (and increasing the probability that it will flourish with your investment) but there is no guaranteed result.

The Devils might also see themselves as an inverse insurance company: With an insurance company, a lot of people give a little bit of money to the company in the hopes that they might get a huge payoff, if they really need it. The company stays afloat through a wide customer base and complicated risk calculation.
The Devils give minor services to a lot of people in the hopes of occasionally getting a huge payoff. They also stay afloat through a wide customer base and complicated risk calculation.

If you consider an insurance company to live via the exchange of goods and services, then, I think, this would Also describe the Devils in this scenario. (Of course, I get that this might just not be the type of "service" that fits your story.)

$\begingroup$The problem with this is that it doesn't fit the narrative and the style. The deal has to be an exchange of goods or services. This answer is giving away something for free, even though it has side effects. But having side effects doesn't mean it's an exchange of goods or services.$\endgroup$
– vszMar 4 '17 at 8:01

An obvious option would be to make a deal for temporary dominion over the soul after death - after all, while you might not be willing to get something in exchange for eternal damnation, you might be willing to make the trade for a year of damnation.

The beauty of this is that the smaller trade seems a lot more reasonable, to the point that, when you get what you want, you're open to the idea of making another trade, and another, and another. And due to the nature of human greed, the more you get, the more you want, and the more you're willing to trade for it.

By the end, you're being offered the full Faustian deal. Basically it's Faustian deal by Creeping Normality. And even if you don't continue all the way to the full Faustian deal, the devils still get the same benefits of dominion over the soul, albeit only temporarily. Since the original deal has some tangible benefit to the devils, and that "dominion over souls" isn't its own reward (that is, it's used for some purpose), then even temporary dominion is beneficial.

Not to mention that people are likely to want to escape any damnation, even temporary damnation, if they can - this gives those people motivation to then act as a kind of finder for the devils. If they can coax someone else to trade a longer-term dominion over their soul, the "finders fee" is the removal of the temporary dominion over the soul of the finder.

But if they successfully do that, then they may realise that they have a business going, and essentially start working on a commission of sorts. Suddenly, the Infernal Corporation has willing humans acting as PR/advertising.

So in the end, in all possible outcomes, it's a win for the Infernal Corporation.

I would suggest the devils focus on people aiming to get into positions of power (political, economical, social, whatever). The only price they ask for their support in this ambition is that the client take one of the devil lawyers as a permanent advisor (and possibly a monetary fee to hide their true intentions). Obviously, should they ever try to get rid of said advisor (who probably passes as human to other people), their status of power would collapse with subsequent negative consequences for the client.

This will seem like a win/win to the client because they get a powerful lawyer out of the deal for a much lower price than otherwise possible. And if the advice is bad, they can always refuse, right? Right?

However, it should be no problem whatsoever for your devious lawyers to convince their clients that, say, ignoring the health regulations with respect to their employees would be a good idea. Or that poor people get way too much financial support already. Or that declaring a war on that one insignificant neighbouring country would in their best interests. Etc.

The key idea is to push someone to the top who they can then manipulate into causing massive suffering for others. You can then combine this with other posters' ideas to then get access to these victims' souls when they're at their most desperate.

Question: (Sorry, I don't have enough reputation to comment yet.)

Would it be possible to get people to sell their soul in exchange for someone else (family members, friends, lover) to benefit? Or would this self-sacrifice render the soul worthless to the devils?

Perhaps the devil's are willing to trade people small, temporary but otherwise 'unobtainable' things in order to entice them into further dealings. What the devils receive for these favors is of no consequence, it can be a small 'sin', something so trivial that a man might reason he does such a comparable thing every day.

But it compromises the man, he must admit to himself that he is indeed corruptible; he has a tear in his moral fabric. The ease of transactions will have him coming back, like a drug addict chasing his fix. And when his hopes and dreams inevitable come crashing down upon him (and they will as the devils only offer things he does not have the means to hold onto), the devils will come to him offering everything in exchange for something he can't every see.

In this model, the initial deals are each considered a loss leader, a product a company takes a loss on in order to entice a customer into further purchases. It is also analogous to an addiction model where the customer is always chasing a large fix.

The long game: Nudging other people closer to giving up their soul

If few are willing to give up their soul, then an indirect approach might be useful. The devils can recognize that those who actually do give up their soul do so under certain circumstances (despair, to save loved ones, etc.). If so, then they need to create those circumstances.

So the demons have two kinds of 'customers'. The first type is one real mark, the ones that with enough manipulation can be made to willingly give up their souls. These may be ones who have contacted the demons as the second category in the past, or totally unknowing victims. The important point is that the demons are in for the long game with these people. They follow them through their entire lives just to create that particular setup where they will have no way out but to call them and offer all they have.

The second type is the bulk of their customers. These people gain minor favors in exchange for doing things that push one of the real marks towards their final destination. Typically they will be entirely unaware of the real consequences of their actions and all of them might not appear to be overtly evil (although that depends on what the particular endgame is). It might be things like delivering a letter, closing their store early, convincing their friend to try a new drug, rescuing someone from a peril or pretty much anything.

This can be nested to any level. Some devils might be setting up organizations, cults, drug cartels, gangs, insiders in governments etc through pawns and favors which can then be used to favor the long-games of the real marks of other devils.

All of it ends with the same thing, people giving up their souls, but the majority of the effort is on the 'enabler structure' rather than the real victims.

The devils could still mandate that people give up their eternal soul, but make it feel less expensive.

One way to do this would be to bundle "immortality" with their wishes, with a carefully crafted definition of immortality (all in the terms and conditions, of course). After all, is eternal damnation so costly if you think you will never die?

Of course, immortality only covers old age, but not death from other causes. And when you have an eternity to play with, you can be confident something will get them eventually.

If the idea is to encourage many smaller, more trivial deals

Simply trade things for cash, with an ongoing subscription fee. This could be marketed as "after sales support", where you promise to continue to fix problems as they arise, so long as it is within the scope of the original deal. But there's a catch - the fee isn't fixed (this is buried in the fine print somewhere). The idea is to grant wishes that feel extremely worthwile and bring many, extraordinary benefits almost immediately, so that the ongoing costs don't feel such a burden. But, if you don't keep up with the payments, it all goes away, your nefarious deeds are exposed, and you will be brought to social, economic, and personal ruin.

That \$10,000 per year in order to kill your political rival seemed great, but now the Devil wants \$50,000 per year. And he's got all those documents linking you to the crime. Before you know it, he's asking for twice your annual salary... but don't worry, there's a way to make it all go away...

Gambling.

If the only commodity of interest to the devils is a soul, but everyone knows that it's too high a price for anything... then what ratio is acceptable?

Take a roulette wheel.

You come in, you ask for a favour. You get the favour no matter what, provided you spin the wheel... and if you win, you keep your 'stake' for another day.

So for a little favour - one number is a 'lose'. And for a big favour... well, that might be a 50/50 sort of a deal. And hey, if you do want to go 'all in' then... well, maybe you've just got one number as your 'get out of hell free'.

But you've always got a chance, and that's how you trade 'fractions of a soul'.

There may be no reward that's worth your soul, but a 1/37 (or 38) chance of losing your soul might be altogether more tempting... because you could, and indeed probably will walk away rich and free. Or save a dear family member, with no consequences...

The appropriate idea has already been mentioned in a different way: The pyramid scheme. It is very simple: Your contract is for your immortal soul but don't worry, you won't actually have to pay it. In fact, it will all be completely free for you! Yes, free 100%. All you need to do is convince two other people to sign the contract with us, and your bond is released, look it's right here in §2.

Make it a win-win (lose-lose, but who cares about losers?) situation. Everyone will sign the deal thinking they are getting a free wish and they have the rest of their lives to trick just two other people into signing the same deal. Easy, right?

Some inspiration (...or something to avoid?) can be found in a story by Robert Louis Stevenson, of Jekyll & Hyde fame. It's about a wish-granting bottle that would doom to Hell the soul of they who owned it at their death. The bottle could be sold, but always at a loss, and the buyer had to be well-informed.

The story has a couple of maybe interesting twists. One wish for riches happens at the expense of the death of near family - causing inheritance of those riches. The bottle is getting to a very low price, which is a problem for buyers. And once one has tried the bottle he later wants it back to fix new problems, so one could argue that some corruption is going on, which should be a general long-term investment for the Infernal Corp. Even, if the repeat-buyer is so desperate, maybe he would get into a new kind of deal directly with the makers of the bottle?

Thank you for your interest in this question.
Because it has attracted low-quality or spam answers that had to be removed, posting an answer now requires 10 reputation on this site (the association bonus does not count).